Question

tinh nhanh 

B= -9/10 . 5/14 . + 1/10 . (-9/2 ) + 1/7 . (-9/10) 

Answer 1

\(B=\frac{-9}{10}.\frac{5}{14}+\frac{1}{10}.\frac{-9}{2}+\frac{1}{7}.\frac{-9}{10}\)
\(B=\frac{-9}{2}.\frac{1}{14}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-9}{28}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-27}{35}+\frac{-9}{70}\)
\(B=-\frac{9}{10}\)